Gianni Belvedere, 24, has been missing since the deadly shooting of his girlfriend and brother outside a San Diego mall

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Gianni Belvedere, 24, has been missing since Monday. His girlfriend, Ilona Flint, and brother, Salvatore Belvedere, were fatally shot in a parking lot outside a mall in San Diego on Christmas Eve morning.

Updated at 6:44 PM EDT on Saturday, Dec 28, 2013

The search continues for a San Diego man missing since the deadly Christmas Eve shooting of his girlfriend and brother near Westfield Mission Valley Mall.

According to the San Diego Police Department, Gianni Belvedere, 24, was last seen Monday around 10 p.m. at his home in San Diego’s Tierrasanta community.

On Tuesday at around 1:15 a.m., Gianni’s longtime girlfriend, Ilona Flint, and his brother, Salvatore Belvedere, were critically shot in the parking lot of Mission Valley mall, just outside of a Macy’s department store. The store was open to accommodate last-minute Christmas shoppers.

Neighbors Shocked Over Deaths of Belvedere, Flint

Neighbors in Tierrasanta are shocked over the deaths of Salvatore Belvedere and Ilona Flint, both 22, shot on Christmas Eve in a parking lot outside Mission Valley Mall. Now, the brother and boyfriend of the victims has gone missing. NBC 7's Lauren Lee reports. (Published Saturday, Dec 28, 2013)

Salvatore sustained gunshot wounds to the head and torso and was transported to a local hospital. He remained in critical condition for several days and on Friday, the SDPD confirmed he had died from his injuries.

Paul Donato, Salvatore's cousin, issued a family statement Friday saying that Salvatore had a rare blood type and was an organ donor. A heart transplant was performed after his death.

Shooting Victim's Brother, Fiance Missing: Family

Gianni Belvedere hasn't been seen or heard from since the shooting on Tuesday morning, his family told NBC 7 News. (Published Thursday, Dec 26, 2013)

"But even through this tragedy, his precious heart now beats in someone else," said Donato. "What better way during the Christmas season to give the gift of life."

The statement went on to say that the Belvedere family is still looking for Gianni.

Mission Valley Mall Christmas Eve Shooting: Images

Both Flint and Salvatore were 22 years old.

According to police, the suspect in the deadly parking lot shooting was described as a male wearing tan pants, between 5-foot-9 and 5-foot-11. A possible vehicle of interest in the case is a 2008 to 2011 dark gray Honda sedan.

Now, three days later, police have shifted their attention to finding Gianni, who is considered a missing person at this point. Family members said Gianni may have also been at the mall at the time of the shooting.

On Thursday, members of both the Flint and Belvedere families made a public plea asking for Gianni to return home.

“Gianni, we need you to come home,” said his sister, Antoinette Belvedere.

Police are asking for the public’s help in locating Gianni. Anyone with information related to his whereabouts or the shooting should contact the SDPD Homicide Unit at (619) 531-2293 or Crime Stoppers at (888) 580-8477.

Earlier this week, family members said they don’t know why Salvatore was at the mall with his brother’s girlfriend on Tuesday morning.

Andre Briones, a friend who worked with Flint at a vintage shop in La Jolla, said Flint had been dating Gianni for eight years. Briones said the Belvedere brothers would take turns picking up Flint from work because she didn’t have a car.

On Friday night, neighbors in Tierrasanta told NBC 7 they were shocked over the deaths of Salvatore and Ilona and the disappearance of Gianni.

According to neighbors, the Belvedere brothers lived on a quiet street and on Madera Rosa Way. Neighbors said Flint lived with the brothers as well.

A resident who wished to remain anonymous said he saw the brothers every day and even hung out with them last week in their garage.

“Just when I came home, [I] just came over, had a couple beers with them and that was it,” said the neighbor.

Though the neighbor said he wasn’t close with the Belvedere brothers, he said the men were always friendly.

“They were great; they were always cool, always nice,” he added. “It’s weird. Especially seeing them every day, and now never getting to see them again.”

Meanwhile, a memorial for Flint is set to take place at La Jolla Shores on Saturday at 6 p.m. A friend said Flint worked at a vintage shop in the area. Flint's mother is expected to attend the memorial.